(1) Field of the Invention
This invention relates to a scanning apparatus, in particular to a scanning apparatus able to reduce the vibration while scanning.
(2) Description of the Prior Art
Nowadays, a variety of business machines are becoming indispensable to the living of human beings. The tasks, such as the transmitting, duplicating, storing, or editing for various information of pictures, text documents, etc., are completed by various business machines. Yet before the data as mentioned are processed, images are scanned in advance and transformed into electrical signals so that data can be further processed.
At present, flatbed is the most popular scanner type. Please refer to FIG. 1A, a schematic of a well-known flatbed scanner. As shown in FIG. 1A., the outer covering of scanning device 1 is like a crate, usually comprising a glass pane and a case and holding a chest inside the covering for mounting various scanning elements. In the scanning device 1, the element for mainly performing scanning is the optical device 10, comprising a light source 101, a reflector 102, a lens 103, and an image sensor 104.
As a document is disposed on the glass pane of the scanning device 1 for scanning, the image to be scanned is placed facing downwards so that the light from the light source 101 may illuminate the text image. Part of the, light is reflected to the reflector 102, then to the lens 103 via a proper angle of reflection, and finally is focused on the image sensor 104. Subsequently, the different brightness of images is transformed into corresponding analog signals, either output directly or delivered to an AD/DA converter to be converted into digital signals for further processing.
In order that the scanning range of the optical device 10 may cover the whole document, it needs to be conducted by a guiding mechanism so that it can scan back and forth in the scanning device. Therefore, as shown in FIG. 1., the optical device 10 is disposed on the guide bar 11 via a loading frame 11 (not shown in the figure), stretching across both sides of the scanning device 1, and is able to move forwards and backwards by the power provided by a power source (not shown in the figure). Apparently, it leads to a significant impact on the quality of the image if the optical device 10 can move smoothly and stably on the guide bar 11 while scanning.
Please refer to FIG. 1B., a schematic of connection between the optic device 10 and a guiding mechanism, comprising a guide bar 11 and a loading frame 12.
The guide bar 11 provides a scanning path in X direction to guide the optical device 10 to move.
The load frame 12 can carry the optical device 10 to move on the guide bar 11. The optical device 10 is disposed above the loading frame 12. The guide slot 121 is below the loading frame 12. The loading frame 12 embraces the guide bar 11 by means of the guide slot 121.
The loading frame 12, driven by the power provided by a driver (not shown in the figure), can move forwards and backwards in the X direction along the surface of the guide bar 11.
The enlarged figure as shown is a lateral schematic for the embrace of the loading frame 12 and guide bar 11. In general, because inaccuracy between the loading frame 12 and the guide bar 11 occurrs during manufacture, both sizes of the loading frame 12 and the guide bar 11 can not meet completely. If the loading frame tightly attaches to the guide bar 11, this will lead to an over-large sliding friction, resulting in trivial abrasion, or yield a high temperature that induces variations. After designing the sizes of both and considering the tolerance, one will prevent the size of the guide bar 11 from being larger than that of the guide slot 121. This leads to a slightly larger opening of the guide slot 121 than that of guide bar 11.
Consequently, a slight gap S occurs between the guide slot 121 than that of guide bar 11. This gap S is liable to cause vibrations when the loading frame moves. This makes images blurred and distorted. More likely, as shown in FIG. 1C., the optical device 10 is not straight-vertically disposed on the guide bar 11, but with a slight offset (an angle a as shown in the figure), which makes image obtained tilt. All the above factors will seriously affect the final quality of images.
Therefore, any effort devoted to getting rid of the above shortcomings so as to improve the scanning stability for the optical device is definitely welcome to all the persons in the art.